Equipment which uses a motor represented by a hybrid automobile, an electric automobile or the like utilizes a power conversion device for energy saving. The power conversion device usually utilizes a semiconductor module. The semiconductor module comprises a power semiconductor element for controlling large current.
The heat value of the power semiconductor element is large when the element controls large current. Since miniaturization or lightweight of a semiconductor module is demanded and the output density tends to rise, the power conversion efficiency depends on a method of cooling the power semiconductor elements in a semiconductor module comprising a plurality of power semiconductor elements.
In order to improve the cooling efficiency of a semiconductor module, a liquid cooling type cooler has been conventionally used. Such a liquid cooling type cooler contains a fin as a heat sink, and cooling is performed by passing a coolant to circulate in the cooler. In order to improve cooling efficiency, a variety of elaborations have been made on liquid cooling type coolers such as increasing the flow rate of a coolant, improving the heat transfer coefficient by micronization and complication of a fin, and improving the thermal conductivity of a material which constitutes the fin.
However, when the flow rate of a coolant in a cooler is increased or a fin has a shape by which an excellent heat transfer coefficient is obtained, a problem that the pressure loss of a coolant inside the cooler is increased or the like is likely to occur. In particular, there is disclosed a cooler which uses a plurality of fins for cooling multiple power semiconductor elements, wherein the fins are provided in series in a flow channel (Patent document 1), and an increase of the pressure loss is remarkable in a cooler having such a constitution. In order to reduce such a pressure loss, a constitution in which cooling efficiency is improved with a low coolant flow rate is needed, and fins are desirably arranged in parallel in a flow channel.
Examples of a cooler in which cooling performance is maintained and pressure loss of a coolant is reduced by arranging fins in parallel in a flow channel include those in which an introduction path for introducing a coolant and a discharge path for discharging a coolant are arranged parallel to each other and a plurality of fins are arranged in parallel in cooling flow channels therebetween (Patent document 2, 3, 4).